// run: $exec < input
#include <iostream>
#include <string>

std::string s;
int a[4];

int main()
{
	std::cin >> s;
	for (int i = 0; i < (int)s.size(); i += 2)
		a[s[i] - '0']++;
	std::string ans;
	if (a[1]) { ans = "1"; a[1]--; }
	for (; a[1]--; ) ans += "+1";
	if (a[2]) {
		if (ans.size()) ans += "+2";
		else ans = "2";
		a[2]--;
	}
	for (; a[2]--; ) ans += "+2";
	if (a[3]) {
		if (ans.size()) ans += "+3";
		else ans = "3";
		a[3]--;
	}
	for (; a[3]--; ) ans += "+3";
	std::cout << ans << '\n';
}

